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Bases estructurales de la transcripción: ARN polimerasa II con una resolución de 2,8 angstroms
P Cramer1, D A Bushnell, R D Kornberg
1Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305-5126, USA.
Science (New York, N.Y.)
|April 21, 2001
Resumen
Los estudios estructurales de la levadura ARN polimerasa II revelan cuatro módulos móviles, incluida una abrazadera crucial para el inicio de la transcripción. También se detallan los iones metálicos en el sitio activo y las vías de salida de ARN.
Área de la Ciencia:
- Biología Molecular Biología Molecular
- Biología Estructural Biología estructural.
- La bioquímica es la bioquímica.
Sus antecedentes:
- La ARN polimerasa II es esencial para la transcripción génica en los eucariotas.
- Comprender su estructura es clave para descifrar el proceso de transcripción.
- Estudios anteriores indicaron un dominio móvil de pinza en la ARN polimerasa II.
Objetivo del estudio:
- Para determinar las estructuras de alta resolución de la levadura ARN polimerasa II.
- Aclarar las bases estructurales de la iniciación y elongación de la transcripción.
- Para identificar los elementos funcionales clave dentro del complejo enzimático.
Principales métodos:
- Se utilizó la cristalografía de rayos X para obtener estructuras con una resolución de 2,8 y 3,1 angstroms.
- El análisis comparativo de diferentes formas de cristales reveló módulos móviles.
- Diferencia El mapeo de Fourier identificó iones metálicos en el sitio activo.
Principales resultados:
- La estructura de la ARN polimerasa II de la levadura comprende cuatro módulos móviles, incluida una abrazadera giratoria.
- Una conformación de abrazadera abierta en la estructura de 2,8 angstroms facilita la entrada del ADN promotor.
- Se observaron dos iones metálicos en el sitio activo, con uno potencialmente intercambiable durante la síntesis de ARN.
- La evidencia sugiere que la salida de ARN se produce cerca del dominio de repetición carboxilo-terminal, vinculando la síntesis con el procesamiento.
Conclusiones:
- Los módulos móviles identificados, en particular la abrazadera, juegan un papel crítico en la transcripción.
- Los conocimientos estructurales proporcionan una base para la comprensión de las interacciones ADN / ARN y la catálisis de iones metálicos.
- Los hallazgos sugieren un acoplamiento funcional entre la síntesis de ARN y la maquinaria de procesamiento de ARN.
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